British Numberphile: - 23 and Football Birthdays [View all]

[MarkCharles]

http://skepttv.tumblr.com/post/17967871109/numberphile-23-and-football-birthdays

What’s the probability that two people on the football/soccer pitch share a birthday? That’s only 23 people (22 players and the ref, as long as there have been no red cards or injuries!!!) and there are 365 days in a normal year.

Dr James Grime explains. Our thanks to Nottingham Forest Football Club.

Website: http://www.numberphile.com/
Numberphile on Facebook: http://www.facebook.com/numberphile
Numberphile tweets: https://twitter.com/numberphile
Videos by Brady Haran

Source:

ANSWER: Slightly greater than a 50% chance that any random 23 people share a birthday.

Another way of thinking about it is that an average public school classroom in America might have 23 people in it. Who shares a birthday there, obviously the same chance of sharing one, unless, of course, two of the people in that classroom are twins, then the odds are already met, but the odds of a third sharing any one birthday with the twins or with another person go down considerably.



Why?